A shape measuring machine known from DE 43 45 094 C2 corresponds to a device of the type referred to in the foregoing, which machine includes a reference system of its own for path correction on guideways that is decoupled from the machine's guiding means and control devices and comprises dimensionally accurate elongate standards disposed in parallel alignment to the individual coordinate axes of slidable carriages and adapted to be scanned continuously by parts movable on the guiding means. The reference system is constituted so as to have a geometry which is long-term stable with little sensitivity to temperature. However, the effort involved in order to achieve the requisite measurement accuracy is considerable in this known shape measuring machine, in terms of both apparatus and measurement expenditure. The reference system is comprised of three standards, each formed by profiled rails of rectangular cross-section carrying scanning tracks on two adjacent lateral surfaces. The first standard is mounted on the machine bed. The second standard is attached to the end of a vertical column in addition to having at one end angle brackets embracing the scanning tracks of the first standard, so that the second standard is coupled to the first standard. Correspondingly, the third standard is coupled to the second standard. Provided at each of the two coupling locations between the three standards are several sensors which detect any relative movement between two standards at their coupling location in terms of their position and direction. The detected values are fed to a computing unit calculating therefrom corresponding correction values for the measurement result or for a spatial position of the probe element. This construction aims to enable the known shape measuring machine to exhibit an improved dynamic behavior and reduced non-productive times and durations of measurement as compared with a shape measuring machine with an extremely rigid machine bed, which is frequently manufactured from granite and supports, through a sliding carriage, the vertical column, which in turn is either a solid or heavy cast or steel welded construction.
From DE 31 50 977 A1 methods and a device are known for determining and correcting guide defects of guided machine parts. It includes determining the relevant guide defects of a measuring machine and approximating them by correcting functions stored in the machine's computing unit. The incorrect results of the coordinate measuring device are then corrected in subsequent measurements by means of the correcting functions. A prismatic reference standard that extends parallel to the guide of a carriage carries on a first and on a second surface line gratings, one of which is two-dimensional. A position measuring system serves to determine the spatial position of a support member fixedly connected to the carriage, which support member has reading heads fitted to it and is guided on the reference standard. The reading heads or the support member are placed directly on surfaces of the reference standard. The support member is thus necessarily in touch with the reference standard, which thus forms a mechanical guide, which is always a disadvantage.
From WO 99/17073 a device is known for the detection of six components of the relative motion of two bodies with one primarily two-dimensional translational basic motion. The bodies are formed of a plate provided with a two-dimensional optical grating and of an element having a plane surface parallel to the plate and several optical gratings as reading head. The element is approximated to the plate in such fashion that the optical gratings enable detection of relative displacements, parallel to the plate, in the X and Y directions through an evaluation of the intensity variations of the reflected light. To detect the distance between the element and the plate, provision is made for at least three distance sensing devices which are of the capacitive, inductive or probe type. The device necessitates a planar standard arranged on the one body with a two-dimensional grating, as well as a plane surface provided on the other body and adapted to be aligned parallel to the planar standard.
GB 2 034 880 A discloses an apparatus equally designed in particular to perform linear measurements in two dimensions. In addition, it provides a carriage movable along guide rails in two dimensions over a base. The carriage includes a surface upon which may be placed an object to be measured. The underside of the surface carries a first optical grating comprising parallel lines extending at right angles to one another. A probe is positioned above the surface. Secured to the base under the carriage are two reading heads for detecting movements of the carriage in two vertical directions.
It is an object of the present invention to provide a device of the type initially referred to, which is less complex in terms of construction and measuring engineering.